Methods and apparatus for recovery of damaged subsea pipeline sections

Abstract

A method of remediation of a wet buckled pipeline uses a Submersible Vehicle (SV), Autonomous Underwater Vehicle (AUV), or Remote Operated Vehicle (ROV) and includes the steps of retaining an end of the buckled pipeline; cutting the buckled pipeline underwater below a damaged section of the buckled pipeline; attaching a termination to the cut end of the buckled pipeline; connecting a hydraulic pump to the termination; and running the pump to pull water out of the pipeline.

The invention claimed is: 
     
       1. A method of remediation of a wet buckled pipeline using a subsea pipeline service skid comprising the steps of:
 retaining an end of the buckled pipeline above water and exposable to a source of surface gas that can enter the end of the buckled pipeline; 
 cutting the buckled pipeline underwater below a damaged section of the buckled pipeline thereby generating a cut end of the buckled pipeline; 
 attaching a valved closure to the cut end of the buckled pipeline; 
 connecting a hydraulic pump to the valved closure and running the pump to pull water out of the pipeline and thereby reduce pressure in the pipeline and draw air in from the surface gas to dewater the severed section; and 
 recovering the dewatered section to a surface vessel. 
 
     
     
       2. The method of  claim 1 , wherein the pump is a high pressure pump having a range of pressure pumping capacity of from 100 to 20,000 p.s.i. 
     
     
       3. The method of  claim 1 , further comprising inserting a dewatering pig into the buckled pipeline above the water and before the source of surface gas. 
     
     
       4. The method of  claim 1 , wherein the valved closure includes a hot stab connection. 
     
     
       5. The method of  claim 1 , wherein the valved closure includes laydown heads. 
     
     
       6. The method of  claim 1 , wherein the hydraulic pump is a triplex pump connected via a flexible coupling to a hydraulic motor. 
     
     
       7. The method of  claim 1 , wherein the hydraulic pump is a positive displacement pump. 
     
     
       8. The method of  claim 1 , wherein the hydraulic pump is mounted on a skid that includes a rigid frame, the rigid frame being attachable via a mounting plate to a SV, AUV or ROV. 
     
     
       9. The method of  claim 8 , wherein the skid includes a buoyancy compensator. 
     
     
       10. A method of recovery of a section of pipeline disposed on a seabed comprising the steps of:
 deploying a Submersible Vehicle (SV), Autonomous Underwater Vehicle (AUV), or Remote Operated Vehicle (ROV) to install a termination head on each of a first and a second end of the section of pipeline; 
 providing a source of gas to the first end of the section of pipeline; 
 utilizing the SV, AUV or ROV to move a Subsea Pipeline Service Skid (SPSS) that includes a high pressure hydraulic pump to the second end of the pipeline and connect the SPSS to the termination head; and 
 utilizing the high pressure hydraulic pump to pull water out of the pipeline and displace fluid in the pipeline with a volume of gas from the gas source, thereby dewatering the pipeline; and 
 recovering the dewatered section of pipeline from the seabed. 
 
     
     
       11. The method of  claim 10 , wherein the high pressure hydraulic pump has a range of pressure pumping capacity of from 100 to 20,000 PSI. 
     
     
       12. The method of  claim 10 , further comprising inserting a dewatering pig in the first end of the pipeline whereby the pig is advanced toward the second end of the pipeline by a combined sucking action of the pump and pushing action of the gas. 
     
     
       13. The method of  claim 10 , wherein the termination head includes a hot stab connection. 
     
     
       14. The method of  claim 10 , wherein the termination head includes one or more laydown heads. 
     
     
       15. The method of  claim 10 , wherein the gas from the gas source is used without a pig.